Pollinator abundance influences pollinator-dependent-crop yield in industrial hemp-cowpea intercrop

Cultural crop-production practices are not only engineered to minimize pest incidence and improve soil health but to also reduce their impacts on floral resources in favor of pollinators’ health. Meanwhile, the burgeoning interest of crop growers to intensively cultivate industrial hemp, Cannabis sativa (Cannabaceae), as a new addition to agroecosystems in the United States may not be inseparable from monocropping and its impact on floral resources. Here, we evaluated how the presence of C. sativa will affect pollinators' choices when intercropped with cowpea (a pollinator-attractive crop); squash (a pollinator-dependent crop), and their yields compared relative to their respective monocrops. Using pan traps, three crops that were grown singly, and as intercrops namely: hemp-cowpea, hemp-squash and squash-cowpea, yielded 1,255 pollinators; of which 41% were wasps, followed by sweat bees (37%), and honeybees (10%); others were bumble bees (9%) and carpenter bees (3%). Pollinators preferably sought intercrops, with more diverse floral resources than the monocrops at the early and the peak periods of flowering; with no significant (p > 0.05) differences in foraging activities among other periods. Hemp intercrops, and squash intercrops significantly had improved yields than the monocrops, except cowpea (p > 0.05). The pollinators’ diversity, evenness and dominance among the six cropping systems had no differences. The implications of these results are that not only will intercropping largely improve crop growers’ returns on their investments, the pollinators’ activities and health owing to the availability of more floral resources will likely improve and perhaps sustainably reverse their decline trends.